1. Field of the Invention
The present invention generally relates to robotics and medical imaging techniques and, more particularly to robotically-assisted surgical systems and other devices incorporating methods for registering image data (both pre-operative and intra-operative) to physical space and for providing feedback, and in particular visual feedback, to the clinician.
2. Description of the Related Art
Computers are increasingly used to plan complex surgeries by analyzing pre-operative Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) scans of a patient.
To execute the surgical plan, it is important to accurately align or register the three-dimensional pre-operative and intra-operative data to an actual location of the patient's anatomical features of interest during surgery.
One conventional technique for performing this type of registration is to attach a stereo-tactic frame or fiducial markers to the patient, and to precisely locate the frame or markers prior to and during surgery.
For example, in the case of a surgery involving a patient's femur, a conventional registration protocol includes implanting three metallic markers or pins in the patient's femur (e.g., one proximally in the trochanter and two distally in the condyles, near the knee). However, the insertion of the pins requires minor surgery. A CT-scan image of the patient is subsequently acquired. By analyzing the CT data, the surgeon decides upon the size and location of the implant that best fits the patient's anatomy. During surgery, the metallic pins are exposed at the hip and knee. The patient's leg is attached to a surgical robot device that then must locate the exposed pins. A registration, or coordinate transformation from CT space to robot space, is computed using the locations of the three pins as a Cartesian frame. The accuracy of this registration has been measured to be better than one millimeter. This conventional registration protocol is described in U.S. Pat. No. 5,299,288 entitled "IMAGE-DIRECTED ROBOTIC SYSTEM FOR PRECISE ROBOTIC SURGERY INCLUDING REDUNDANT CONSISTENCY CHECKING" by Glassman et al., and incorporated herein by reference.
However, using such pins as markers is not always desirable, as they may cause significant patient discomfort, and the required surgical procedure to insert and subsequently remove the pins is inconvenient and costly to the patient.
An alternative registration technique is to perform anatomy-based registration that uses anatomical features of the patient (e.g., generally bone features), as markers for registration. Conventional methods for performing anatomy-based registration are described in "Registration of Head CT Images to Physical Space Using a Weighted Combination of Points and Surfaces" by Herring et al., in IEEE Transactions on Medical Imaging, Vol. 17, No 5, pages 753-761, 1998 and in U.S. patent application Ser. No. 08/936,935 entitled "METHODS AND APPARATUS FOR REGISTERING CT-SCAN DATA TO MULTIPLE FLUOROSCOPIC IMAGES", filed on Sep. 27, 1997 by A Gueziec et al., each of which is herein incorporated by reference in its entirety.
Once the registration has been performed, it is important to provide the clinician with means to assess the registration, allowing him or her to validate, reject or improve the registration (and the surgical plan). A system and method for advising a surgeon is described in U.S. Pat. No. 5,445,166, entitled "SYSTEM FOR ADVISING A SURGEON", by Taylor, which is herein incorporated by reference in its entirety. Taylor describes a system for guiding the motions of a robot, or of a positioning device controlled by motors, and teaches how audio feedback and force feedback can be provided to a surgeon. Taylor also describes a visual adviser allowing comparison of the surgical plan with its execution. The system taught by Taylor optionally uses a camera at the end of a surgical instrument that sends an image to the graphics adapter, optionally mixed with graphics output of the computer.
A conventional technique for simulating a post-operative X-ray image is described in "An Overview of Computer-Integrated Surgery at the IBM T. J. Watson Research Center" by Taylor et al., in IBM Journal of Research, 1996, which is herein incorporated by reference in its entirety.
Thus, conventional techniques are useful for registering three-dimensional pre-operative and intra-operative data to an actual location of anatomical features of interest during surgery, and to provide advice to the surgeon. However, none of the conventional techniques teaches how to simulate a post-operative condition depending upon the registration of image data to physical space, by fusing intra-operative images with registered pre-operative data, and generating new images.
In Taylor et al., the simulated post-operative X-ray image is generated using only pre-operative CT (Computed Tomography) data. Herring et al. do not teach how to evaluate the registration accuracy intra-operatively.
Although Glassman et al.'s and Taylor's systems compare a surgical plan and its execution, neither Glassman et al. nor Taylor teaches how to simulate the outcome of a surgical plan prior to the actual execution of the plan. With Taylor's system, a surgeon can take corrective measures to minimize the effects of a wrongful execution of the plan, but cannot make a decision before any execution of the plan and therefore cannot prevent all errors before they occur.
Further, the information produced by Taylor's system for advising a surgeon is not represented in the form of conventional medical media (e.g., such as X-ray images) and require an extra burden on the surgeon in order to interpret and evaluate this information.
Thus, it is believed that conventional techniques do not exist (or at the very least are inadequate) for (a) providing the surgeon with post-operative evaluations prior to surgery, that are obtained by merging intra-operative image data and pre-operative data, and (b) presenting such evaluations in a standard clinical fashion (e.g., such as augmented X-ray images) that is natural for a surgeon to interpret.
Other problems of the conventional systems and methods include the limited availability of 2-D/3-D registration methods in conventional art systems for advising a surgeon and the 2-D/3-D registration postdates.